A unifying hypothesis of the projects proposed in this grant is that reactive oxygen species (ROS) play important roles in mediating both normal and pathophysiological vascular events. The purpose of the Imaging Core will be to provide resources and support to participants of the PPG for brightfield and fluorescence imaging and fluorescence activated cell sorting (FACS) measurements as experimental tools to test this hypothesis using the following methods: (a) the detection and measurement of the fluorescent products of free radical oxygen and H2O2 within intact vascular tissues and/or cultured cells from transgenic animal models; (b) the identification of ROS-producing cells in vascular tissue and cultured cells using cell-specific fluorescent probes or indirect immunofluorescence of cell-specific antibodies; and (c) the detection, measurement and histological analysis of cell proliferation, cell hypertrophy, and atherosclerotic lesion size in animal models. The addition of the Imaging Core facility will significantly enhance the ability of project leaders to visualize the locations of ROS production under a variety of experimental or pathological conditions both in tissue culture and in intact tissue and to correlate these morphological data with other more quantitative methods that measure ROS such as electron spin resonance (ESR) spectroscopy. Specifically the Imaging Core will: 1. Provide expertise, facilities and training for individuals in performing immunocytochemistry, immunohistochemistry, and histology of vascular tissues, including microscope usage and computerassisted analyses. 2. Assist with quantitative measurements of free radical oxygen and H2O2 production using flow cytometry.